Method of recovering well fluids



Nov. 11, 1941. J. P. WALKER 2,262,744

METHOD-OF RECOVERING WELL FLUIDS Filed Feb. 18, 1959 day Q. Walker are sometimes referred to as condensates.

Patented-Nov. 11, 1941 2,262,744 METHOD or m-zcovnnmc WELL FLUIDS Jay P. Walker, Tulsa, -kla., assignor toEureka Process Corporation, Tulsa, Okla., a corporation of Delaware Application February 18, 1939, Serial No. 257,046

7 Claims. (01.

This invention relates to new and useful improvements in methods of recovering well fluids.

The invention has particularly to do with certain improvements upon theinvention set forth in our Letters Patent No. 2,080,351, issued May 11, 1937, and upon the invention disclosed in our application for Letters Patent filed August 12, 1938, Serial No. 224,468.

As recited in the foregoing patent and appli- I cation, the hydrocarbons which are processed occur in vaporous form, or in solution with' 'the natural gas, usually only under high pressures within the pressure range of retrograde condensation, and at temperatures in excess of 100 degrees F. These are natural vapors, and so far as is known, have only been found in' a native state or formation and in commercially recoverable quantities, since wellshave been drilled into the deeper pools, usually deeper than four thousand feet. I

These wells for want of a better term have been called, in the industry, distillate" wells, probably because thesegaseous vapors or fluids when converted or processed to a liquid phase, have some of the characteristics of common hydrocarbon distillate's. These wells are also called combination" wells because they may produce some liquids, although the well stream is predominantly gas or gaseous, frequently comprising up to 98 per cent methane or ethane gas.

It has been found that by cooling or reducing the pressure, or by both cooling and pressure reduction of these vaporous or gaseous fluids,-

much more of the liquefiable content is condensed or recovered under high pressures, and the liquefiabie fractionsso condensed from wells It follows from the foregoing analysis that distillate wells apparently exist because of retrograde eous fluids have been converted to the liquid phase, and recovered as liquids, by admixing withthe well stream a cold liquefaction liquid. The

liquefactionliquid has preferably been obtained duction substantially to the retrograde condensation range.

The particular pressure at which the retrograde condensation range begins is somewhat controlled by the composition of the liquids in solution with the natural gas. While some liquids may vaporize or go into solution with the gas at a pressure as low as 650 pounds, other liquids will not vaporize until a much higher pressure is reached. When handling one particular natural gas, the retrograde condensation range may begin at 650 or 700 pounds, while with another natural gas the retrograde range may not begin until 800 or 1,000 pounds, oreven higher, are reached. At this time, it would be difficult to limit the maximum pressure of the retrograde condensation range. When processing, within such pressure range, cooling of the gas has much to do with the recovery of liquids. As heretofore practiced, the liquefactionliquid has to a large extent been artificially cooled and while artificial or extraneous cooling is highitation and agglomeration are cooled without the use of artificial or extraneous means; or wherein only a portion of the cooling is done with artificial or extraneous means, whereby economical cooling and improved recovery may be accomplished.

Another object of the invention is to provide a hydrocarbon liquid recovery method wherein a liquefaction liquid is provided which has been denuded of gas to such an extent as to make a more stable and efllcient liquefaction liquid; or which liquid has been denuded of gas as well as certain of the more volatile or unstable hydrocarbons so as to provide a liquefaction liquid capable of absorbing greater quantities of liquefiable fractions and thus making for increased recovery of desirable hydrocarbon liquids.

An' important object of the invention is to provide a method of the character described wherein the free water, flowing in the well stream,

which water may be augmented by cooling and condensation, is extracted as a preliminary step;

of dehydrating fluid to inhibit the well stream against the formation of gas hydrates.

One of the principal objects of the invention is to provide a method of the character described wherein the well stream is preferably cooled or manipulated to condense or precipitate some of the heavier; or higher boiling-point hydrocarbons, butwparticularly wherein the hydrocarbon liquids, flowing from the well and augmented by said? condensates; are extracted for use as a liquefactionliquid as well as to quickly and economically, recover them from the well stream.

A further object. of the invention is to provide an. improved method wherein the uncondensed or fixed gases, such as methane and ethane, and in-. some instances some of the lighter or more volatile hydrocarbons: may be readily separated-i firom therecoyeredi liquids; which contain; mi'sci-- ble gases. in solution, and such. recovered? liquids subjected: toa sudden or rapid pressure; reduc tion, whereby gas in. solution. is. quickly flashed off, or so quickly released from solution, as. togreatly reduce the temperature of the liquid; the degree of. cooling depending upon, the amplitude of. the pressure reduction and pressure. drop and the particular hydrocarborrcomposition of the liquid. The relatively small amountof gas flashed ofi', may usually be readily disposed of, as for fuel or lease purposes. 'One advantage of this method is that the gaseous well stream may be processed within the retrograde pressure range of condensation and the uncondensed or denuded fixed gases recovered at a high pressure within said range, so as to be returned to a sub-surface reservoir without expensive recompressing. The pressure of the recovered liquids may be reduced below the retrograde condensation range, well down into the low pressure range without efiecting the preceding steps of the method.

A further object of the invention is to provide a method wherein the recovered liquids. may be carried through a pressure reduction which will cool the liquids to a low degree, possibly as low as 20 degrees F. or lower, whereby a portion of the liquids may be delivered to the stock tanks substantially denuded of undesirable gases, thus producing a'more stable product. The other portion of the recovered liquid may be utilized as a cold reflux. The pressure of this reflux is raised sufl'iciently to inject it into the well stream. The ratio of this injected cold reflux to the amount of native liquid recovered from the well stream, may run as high as 100 to 1,.but these figures are subject to a wide range of variation, depending upon the hydrocarbon composition of the well stream and the recoveredliquids.

Still another object of the invention is to provide a method wherein the gas, insolution is flashed oil? or released from the recovered liquids to cool them, and 'a portion of such liquids is carried through a pump to build up the pressure sufiiciently to recirculate it as a reflux, or wherein the reflux which has been cooled as described is carried through a further cooling step, either vide a method wherein a cold reflux medium is 70 produced which has been denuded of the more volatile or lighter fractions, such as 'ethanes and methanes, and in some cases, even propanes and some butanes, by flashing liquids recovered from medium will b so thoroughly denuded, as well as cooled, that when introduced into the flowing well stream, it becomes a much more eflicient medium for absorbing orconverting light or gaseous vapors into a solution phase, so as to be again flashed, thus making for continuous cooling.

Apparatuses designed for carrying out the method will be hereinafter described, together with: other features of the method, and reference is: mad to the accompanying drawing as illustrating such apparatuses, and wherein:

Figure 1 is a diagrammatical view of an apparatus for carrying out the method where dehydration is not used, and

Figure 2 is a diagrammatical view of another apparatus for carrying out the method.

In the drawing, the letter A designates a flowing well of the character described. These wells are found in various localities at depths, usually more than three thousand feet, many having a depth of 8,000 feet and deeper. The pressures in the sub-surfac reservoirs may range from approximately 650 pounds per square inch to more than 4,000 pounds per square inch. Certain liquid constituents which at a lower pressure are found as liquids, apparently go into solution in the gas at higher pressures because of the high temperatures, as well as the highpressures. The lower limits of the pressure range of retrograde condensation, or the pressure at which such range begins, varies according to the composition of the hydrocarbons. Such pressure range has not been found below 650 pounds per square inch, but it may begin there or at 800 or 1,000 pounds, or even higher. The upper limits of such retrograde pressure range have not been definitely established.

The shut-in pressur of the well will be somewhat less than the reservoir pressure. The temperatures of the well fluids in the sub-surface reservoir and at'the well head may vary from approximately 100 degrees F. to 185 degrees and higher, when flowing under high pressure from the well; such high pressures ranging from 1,000

. pounds to 3,000 or 4,000 pounds and higher. All

of these figures and measurements aresubject to variation and are based upon data and infor-. mation available at thistime. Future developments may make marked changes and the invention is not to be limited by these figures and measurements. The method as herein set forth has operated successfully in the recovery of the particular hydrocarbons sought.

The well stream in flowing from the reservoir up the well bore or pipe to the well head, will as a rule undergo some physical changes. heat exchange brought about by temperature reduction and contact with the progressively cooler well pipe and earth heat exchange will cause some of the products in vapor phase to be converted to a liquid phase, and this applies vto water vapors as .well as hydrocarbon vapors.

Frequently, if not usually these vapors will be more or less composed of the heavier hydrocar-. bons. These condensates precipitated by heat exchangeinthe upstream flow 'in the well will continue 'to flow with the well stream as free water and free hydrocarbon liquids, so that when the stream discharges from the well the free a high pressure gas .separating step, from such liquids will be entrained or flowing with the gase- The In the wells which could be profitably handled,

under this method, it has been found that the total recovered liquid,by volum'e, has ranged from approximately one-half gallon to more than three gallons per thousand cubic feet of gas. The

recovered liquids, after the unstable gases have been separated, are in some instances, marketable as low grade motorfuel, rankingas what is now known as "third grade gasoline."

The well stream is conducted through a pipe l (Figure 1) from the well. When'the pressure is very high, as from 1,500 to 4,000 pounds per square inch, it may be desirable to reduce it to some extent, usually notbelow 1,200 to 1,500 pounds per square inch; and for this purpose a regulating valve or choke II is connected in the pipe 10. The valve ll may be left wide open or it may be used to reduce the pressure. If the valve H is left wide open, the pressure may be reduced at a later step. Precooling of the well stream is often desirable and, for this purpose, we have shown a cooler B, which for'. economical reasons may be a water cooler. This cooler is connected in the pipe It], so that the well stream flows through the same. This cooler may be omitted and no precooling performed.

Suitable means for e'xtractingwater or other dehydrating apparatus as a water knockout C, may be connected in the pipe l0 after the cooler B, as is shown in the drawing. The well stream as a rule, aside from its water content, will include fixed gases, such as ethane and methane,

free hydrocarbon liquidswhich are of the same characteristics and components as the distillates or condensates to be recovered and constitute a part thereof, and gaseous vapors or fluids, all entrained insaid stream.

The problem is not only to recover the liquefiable fractions from the vapor phase or gaseous fluids, but to stabilize the entrained'hydrocarbon liquids so that they will not revert to the vapor phase and be carried off with the tail or residual gas after separation of the recovered liquids amounts of the liquefaction fluid are introduced, but under all conditions cooling, which results in condensation is important.

The denuded liquefaction fluid'r'ecovered and cooled as hereinafter'described, may be admixed with the well stream at any suitable point. Up to the point of admixture the well stream may be referred to as such, but from this point ,it will be hereinafter designated in this description as the agglomerated stream, although it is in actuality the well stream with the reflux admixed "therewith, andmay be said to be in the state of condensing the liquefiable constituents ofas preparing the same for condensing. In Figure 1, the pipe l2 connects with a tank or liquedenser D, which as stated may have any suitable construction, however, it is desirable to provide some sort of admixing means, such as baffles l3, which will cause the liquefaction liquid and the well 0r gaseous stream to thoroughly admix. The liquefaction liquid may be introduced into the liquedenser or tank D through a pipe [4 which is connected to the pipe l2 in advance of a choke l5, which is also connected in the pipe [2 adjacent the tank D; The pipe [4 includes a cut-off valve I4. It may be desirable to introduce the liquefaction liquid. or reflux at some point between the well A'and the liquedenser D and for this purpose a pipe I6 including a cut-off valve I1, is illustrated as extending from the pipe l4 to the pipe I0. Either of the pipes M or l6 may be omitted, or if one is to be used-the cut-off valve therein is opened and the cut-off valve in the other pipe is closed. Of course, it will be necessary to build up the pressure of the refiuxsufliciently to introduce it into the well stream.

or not the stream will reach the choke I5 at such a high pressure that a pressure reduction at this point will aid materially in reducing the temperature of the stream, particularly when the cold reflux is introduced. As an example the well may produce at 2,800 lbs. and the valve Il may be'adjusted to cut the pressure to 2,000 lbs., or it may not be reduced at this point. The choke may be set to reduce the pressure to 1,100 lbs. Such pressure reduction will result in .cooling of the stream and condensing of liquefiable hydrocarbon constituents.

As has been pointed out, the primary wall stream of "these distillate type of wells is substantially composed of free gases not subject to appreciable liquefaction under high pressures and prevailingly high temperatures, as well as fractionsin vaporous form which are liquefiable,

ture best designed for commingling' the liquids and fluids of the stream.

The denuded liquefaction liquid is composed of hydrocarbons which have been recovered from the well stream and while it may not have exactly the same composition as the native distillate liquids or fractions to be recovered it will include hydrocarbon components of substantially the same composition as such liquids.' If admixed with' the gaseous well stream in quantities,

which may be greatly in excess of the amounts inherent to the stream so that greater surficial contact and greater cooling thereby is effected,

and other fractions in the liquid phase. These components prevail in a state in which the vaporous and liquid phase fractions which have notbeen condensed are highly dispersed or atomized. e I

In the process of admixing, a major change in the character of the well stream fluids takes place-in the form of an increased liquid content which results in a unification of the highly atomized or dispersed-liquid particles in the primary; well stream fluids with the more massive liquid particles of the liquefaction liquid. During. this step, in which the unification of the moremas'sive liquid particles takes place, the resultant liquid and gas admixture is prepared for separation of the more volatile gases, which is efficiently accomplished, due to the fact that greater proportions of the highly dispersed liquefiable particles have united or combined with the more massive liquid particles of the medium.

; During the process of admixture the cooling of the fluids which will take place will further increase the recovery of liqueflable fractions from i i the combined fluids, due to the condensing which takes place. 5

The fluids enriched by the liquefaction liquid flow from the liquedenser D under reduced temperatures and high pressure which is usuallyabove 650 poundsbecause the well stream is discharged at pressureswithin the range of retrograde condensation and unless reduced at the well head may flow at considerably more than 650 pounds and frequently above 1,000 pounds. The admixed stream flows from the liquedenser through a pipe l8 which may includea valve IS. The stream flowing through this pipe has a much greater liquid content or liquid-to-gas ratio than the well stream as it flows from the well. During this flow the hydrocarbon liquids and 1 the .liqueflable fractions which have been and are being precipitated or condensed will aggloma hand valvev or a regulating valve or a choke so that if it is desired to regulate the pressure of the stream entering the separator, such regulation may be accomplished, however, the valve 20 may be omitted entirely.

- It is one of the theories of retrogradecondensation, as hereinbefore explained, that reducing the pressure within the retrograde range "causes precipitation of liqueflable constituents which are in a vapor phase. This is also spoken of as condensing by pressure reduction and is more or less efl'ective without change in temperature, except such change as would naturally result from reduction in pressure.- The conversion of the liqueflable constituents from the vapor state to the liquid state is increased by cooling the gas and .particularly where cooling is coupled with pressure reduction. This invention contemplates cooling and pressure reduction within the retrograde range throughthe step ;of separating. the liquids from the gas. While temperature reduction and pressure reduction alone will produce the recovery of liquids, tests have shown that by mixing a cold liquid with the gas for cooling the same, further recovery is accomplished because otsuch admixing. In view of the foregoing, it becomes obvious that as uncondensed" or denuded gases.

from 85 to 95% of the original well stream and will readily separate and pass out through the pipe 2| at a pressure determined by the seating of the valve 22. Such gases may be referredinto Be g recovered at a high pressure they may be marketed or used as is found profitable, or they may be returned to the ground under inexpen hereinafter pointed out. The gas which remains in solution in the liquids recovered in the separator E will also depend somewhat upon the pressure atwhich the separation is made, but where separation is carried out at high pressures which are withinthe retrograde condensation range, there will always be in solution sufficient gas to enable the carrying out of the method of this invention. A liquid discharge pipe 23 extends from separator E and includes a float-controlled outlet valve 23. This pipe extends to a flash tank F and may include a pressure reducing valve 25. Usually the liquids will be discharged from the separator under a pressure in excess of 700 or 800 pounds and more frequently in excess of a thousand pounds, however, the invention is not to be limited to these figures. Assuming that the liquids were discharged under a pressure of 1,000 pounds and possibly at a temperature of 40 to 80 degrees, the pressure reducing valve 25 could be set to reduce the pressure to a degree anywhere below the retrograde condensation range. However, in order to pansion will take place, whereby the tempera-' ture of the liquid will be greatly reduced. By

liquefiable constituents may be recovered from 7 high pressure gas flowing from the well at relatively high temperatures, in three modes or steps, as follows: by reducing pressure; by cooling; or by admixing a kindred liquid with the gas which is preferably cold or by a combination of any from the top lbs. or within the retrograde condensation range.

The gases to be separated will probably represent this pressure reducing or flashing step the temperature of the recovered liquids may be reduced to as low as 20 F. or even. lower. gas which is liberated or flashed off in the tank F is carried ofi through a pipe 26 which includes a pressure regulating valve 21, whereby the desired back pressure is held upon said tank. The amount of gas, as hereinbefore stated, which is discharged through the pipe 26 will be negligible when compared with the wolume discharged through the pipe 2|. In practically every location where a plant is established, suit-' able use will be found for the gas discharged from the pipe 26 and consequently will not be wasted; or it may be compressed and returned to the formation.

A pipe 28 leads from the flash tank and includes a float-operated valve 29, all of such valves herein illustrated preferably being of the dia-" phragm operated type so as to operate at various pressures, particularly where operation is required under high pressure. The recovered liquid which is discharged through the pipe 28 will be more or less stable because of the quantity oil gas which has been flashed off. These liquids may be conducted to, storage tanks or to any other point of disposal and will not require th usual weathering and will be substantially Thefree from the usual disturbances due to the presence of gas in solution, particularly the more volatile gases. Liquids recovered under this method will not suffer as much loss by evaporation and yet will contain enough high volatile constituents to make the product useful for the purpose for which it is recovered, such as a' upon preceding temperatures and pressures as well as the particular composition of the recovered liquid. Reflux liquid has been discharged from th flash tank at F. but this degree is given merely as an example. This cold denuded reflux is conducted by the pipe 30 to a pump G where the pressure of the reflux is raised sufficiently for admixing it with the gas stream.- While pumping may slightly raise the temperature, such a "rise will be negligible. The repressured reflux is discharged through a pipe 32 which connects with the pipes l4 and I6, as hereinbefore described.

This method provides a cold reflux without artificial or extraneous cooling at a low cost. Furthermore, the flashed reflux becomes a very excellent medium for absorbing or acquiring from the gas stream, large or small quantities of methane, ethane and small amounts of other valuable constituents which are in the vapor phase or are in solution with the liquids flowing with the gas stream. These gases when and as acquired, particularly under these high pressures, and when flashed to greatly reduced pressures, inherently cool the liquids from whence they are flashed;v and this cooling is, therefore, in proportion in each case to the amount of reflux circulated and also in proportion to the pressure and presence of said gases in the agglomerated liquids. From this it follows that the amount of cooling desired may be controlled to some extent by the amount or quantity of denuded reflux which is circulated in the flow stream because of the temperature variation which results. This method provides a wide variation in temperature of theagglomerated flow stream, thus inherently providing cooling over a wide range of easy regulation.

It cannot be too strongly pointed out that temperature reduction plays a most important part in this recovery method and that the admixing of a liquefaction liquid augments therecovery which is proportionately due to cooling. Cooling causes condensation whereby liquefiable constituents are condensed. In some localities difliculty will be experienced with the formation of gas hydrates whereas in other flelds there will be no hydrate trouble; The formation of hydrates, of course, depends upon the'degree of temperature to which the gas stream is reduced and particularly upon the critical temperatures of the components of said stream; In many instances i the dehydrator C will be adequate to remove water and prevent the formation of hydrates and in some cases even the dehydrator may be disposed of. If hydrates should occur there are many ways of taking care of the situation, one of which is exemplified in our copending application flled August 12, 1938, Serial No. 224,468.

In some localities where daily atmospheric temperatures are not high it may be necessary to insulate the pipe lines,particularly those through which the stream' flows after leaving the dehydrator C and better results may be obtained from insulating all pipe lines. It may be found advisable'to bury the lines in the ground as well as to insulate them. This practice may be variedto suit conditions. It has been found that in some instances it is desirable to cool the reflux to a degree lower than can be obtained in the flash tank F. v

Where a lower, temperature is desired than can be obtained by flashing in thetank F, it has been found expedient to connect in the pipe 32 a. heat exchanger or cooler H, as is shown in Figure 2, which may employ any suitable cooling means as cold water, cold gas, ammonia or the like.

Such cooling will augment the cooling done in possible to use a colder heat exchange medium in the cooler B and cool the well stream .to a lower degree at this point and to connect the dehydrator C in the pipe II) in advance of the cooler 3. Of course, where the cold reflux is introduced into the line l0 through the pipe H5 in advance of, the cooler B the well stream will be cooled by such admixture. Further cooling will result where the pressure is reduced at the choke l5. It is' pointed out that pressure reductions may take place at the valve II or in the tank D by reason of the choke l5 or in the separator E by reason of the valve 20 or at any one, two or three of these points. The arrangement is purposely made flexible in order to meet various conditions; however, this particular invention depends upon the flashing for cooling the reflux as its distinguishing feature.

What I claim and desire to secure by Letters Patent, is:

remove entrained moisture while said stream is still under high pressure, extracting hydrocarbon liquids from said stream and maintaining said stream under high pressure, rapidly dropping the pressure of the separated liquids from a high pressure within the retrograde range to a low pressure below said range to cool the liquids, carrying oil a portion of the liquids as recovered liquids, separately carrying 011 the flash gas resulting from dropping the pressure-0f the separated liquids at a controlled pressure, and recirculating the remaining liquids in contact with said gaseous well stream as a liquefaction fluid.

2. The method of recovering desirable liquefiable constituents from a naturally gaseous well stream which initially flows at a high pressure and temperature within the retrograde conderis sation range of said constituents which includes, conducting a flowing stream under high pressure and relatively high temperature from a well, admixing the stream with large quantities of a liquefaction liquid which has been precooled to a low temperature at which maximum agglomeration of the liquefiable fractions in said stream may be accomplished and below the critical degree at which gas hydrates are formed, extracting the free hydrocarbon liquids from said stream at a temperature below that at which gas hydrates form and maintaining said stream under high pressure, rapidly dropping the pressure of the separated liquids from a high pressure within the retrograde range to a low pressure below said range to cool the liquids, separating and carrying off flash gas resulting from dropping the pressure of the separated liquid at a controlled pressure, carrying oif a portion of the liquids" as recovered liquids, and recirculating the remaining liquids as the liquefaction fluid.

3. The method of recovering desirable liquefiable constituents from a naturally gaseous well stream which initially flows at a high pressure and temperature within the retrograde condensation range of said constituents which includes, conducting a flowing stream under high pressure and relatively high temperature from a well, admixing the stream with a liquefaction liquid at a minimum temperature at which maximum agglomeration of liqueflable fractions may be at a'controlled pressure below 150 pounds, and

recirculating a portion of said liquid as the liquefaction medium,

4. The method of recovering desirable liquefiable constituents from a naturally gaseous well stream which initially flows at a high pressure and temperature within the retrograde condensation range of said constituents which includes, conducting a flowing stream under high pressure and relatively high temperature from a, well, admixing the stream with a liquefaction liquid at a minimum temperature at which maximum agglomeration of liquefiable fractions may be accomplished and at a degree Fahrenheit below the critical degree at which gas hydrates are formed, whereby maximum recovery of hydro.- carbon liquids may be effected, extracting hydrocarbon liquids from said stream, maintaining said stream under high pressure, rapidly dropping the pressure of the separated liquids from a pressure in excess of 600 pounds to less than 150, whereby the gas in solution is quickly released and the temperature of the liquids is reduced to a degree Fahrenheit below the freezing point of water, separately carrying oil the released gas at a' controlled pressure below 150 pounds, carrying off a portion of the cold liquids as a liquefaction liquid, raising the pressure of the cold liquefaction liquid to above that of the flowing stream, and introducing the repressured cold liquefaction liquid into the said stream as the liquefaction liquid.

5. The method of recovering desirable liqueflable constituents from a naturally gaseous well stream which initially flows at a high pressure and temperature within the retrograde condensation range of said constituents which includes, conducting a flowing stream under high pressure and relatively high temperature from a well,.

extracting the free hydrocarbon liquids from said stream and maintaining said stream under high pressure, rapidly dropping the pressure of the separated liquids from-a high pressure to a'low pressure to denude the liquids of gas, separately carrying 011' the flash gas resulting from dropping the pressure of the separated liquids at a controlled pressure, carrying off a portion of the liquids to storage, and recirculating and injecting the remaining denuded cool liquids into the well stream, whereby liquefiable fractions in the well stream .are precipitated as liquids and said denuded liquefaction medium more readily absorbs gaseous products from said stream and holds them insolution.

6. The method of recovering desirable lique-- fiable constituents from a natural gaseous stream which initially flows at a high pressure and temperature within the retrograde condensation range of said constituents which includes, cooling said stream, separating uncondensed gas from the condensed liquids of the stream at av high pressure within the retrograde condensation range of the said constituents, rapidly reducing the pressure from said retrograde range. to a low pressure below said range to cool the liquids, separately carrying off the flash gas resulting from dropping the pressure of the separated liquids at a controlled pressure, carrying off a portion of the cooled liquids, and recirculating said portion of the cooled liquids in the-gaseous stream to cool the same and to condense and recover liquefl'able constituents therefrom.

7. The method of recovering desirable liquefiable constituents from a natural gaseous stream which initially flows at a high pressure and temperature within the retrograde condensation range of said constituents which includes, cooling said stream, separating uncondensed gas from the condensed liquids of the stream at a high pressure within the retrograde condensation range of the said constituents, rapidly reducing the pressure from said retrograde range to a low pressure below said range to cool the liquids, separately carrying off the flash gas resulting from dropping the pressure of the separated liquids at a controlled pressure, carrying off a portion of the cooled liquids, further cooling the portion of said liquids which is carried ofi, and recirculating said portion of the cooled liquids in the gaseous stream to cool the same and to condense and recover liquefiable constituents therefrom.

JAY P. WALKER. 

